1. Field of the Invention
This invention relates to a switching unit fixedly attached on a spoke portion of a steering wheel in a motor vehicle and, more particularly, to a switching unit for a steering wheel which is provided with a switching member on the front side and a switching member on the back side which are mutually integrated and electrically connected.
2. Description of Related Art
According to a conventional switching unit for a steering wheel, a switching member on the front side and a switching member on the back side are attached for mechanical integration on a specific bracket, and are electrically connected by wiring. The bracket of the integrated switching unit is fixedly attached to a core metal of the spoke portion of the steering wheel, so that the switching member on the front side may be mounted on the front side of the spoke portion and the switching member on the back side may be mounted on the back side of the spoke portion as viewed from the driver""s seat of the motor vehicle.
As another example of conventional switching unit, there also has been proposed that the switching member on the front side and the switching member on the back side are separately secured on the core metal of the spoke portion of the steering wheel, then are electrically connected by a wiring harness.
The switching unit for the steering wheel is usable as a push-to-operate switch for performing up- and down-shifts during driving in DRIVE range, and also as a switch for controlling an air-conditioning system and a car phone, and furthermore as a horn switch.
In the former of the above-described conventional arts, the switching unit formed in advance by assembling the switching member on the front side and the switching member on the back side into one unit is securely attached on the spoke portion of the steering wheel. It is, therefore, necessary to attach these switching members to a bracket so formed as to make it possible to hold the core metal of the spoke portion. In this case, there is such a disadvantage as a lowered degree of design freedom because of the shape and size of each switching member. Furthermore, as a modification of the art, both switching members are integrally formed in the status that one of the switching members can be fitted in a through hole provided in the core metal of the spoke portion of the steering wheel. In this case, the shape and size of each switching member are liable to a restriction. Moreover, the provision of a large through hole in the core metal of the spoke portion presents such a problem that the mechanical strength of the spoke portion will be largely deteriorated.
In the case of the latter, the switching member on the front side and the switching member on the back side are separately secured on the core metal of the spoke portion of the steering wheel, and there is no fear of lowering the degree of design freedom and deteriorating the strength of the spoke portion. In this case, however, it becomes necessary to perform, in a narrow space on the back side of the steering wheel, the electrical connection of both switching members by the wiring harness after installing them on the spoke portion, resulting in a deteriorated facility of installation.
In view of the above-described problems inherent in the heretofore known arts, it is an object of this invention to provide a switching unit for a motor vehicle steering wheel which facilitates mechanical and electrical connection of the switching members both on the front and back sides, with little restriction to their shape and without deterioration of the strength of the spoke portion of the steering wheel.
The above-described object of this invention is accomplished by the following constitution. That is, the switching unit fixedly installed on the spoke portion of the motor vehicle steering wheel is provided with a switching member on the front side and a switching member on the back side which are mutually mechanically and electrically connected when mounted on the spoke portion. Electrode portions are located in opposite positions of the switching members. One of these electrode portions is an elastic electrode portion which elastically deforms. In the integrated form of these switching members, the elastic electrode portion as one electrode portion deforms into elastic contact with the other electrode portion.
According to the switching unit of such a constitution, there is no need to integrate the switching member on the front side and the switching member on the back side prior to installation to the steering wheel; therefore, the switching unit is little restricted in shape and size and has a high degree of design freedom. Furthermore, in the mechanically integrated switching members, the elastic electrode portion comes into elastic contact with the other electrode portion, thereby making electrical connection. Therefore, it is possible to dispense with such a complicated operation that the switching members are electrically connected by a wiring harness after installation to the steering wheel. Furthermore, since there is no need to form a through hole in the spoke portion of the steering wheel for installing the switching unit, the switching unit will not decrease in mechanical strength.
On addition to the constitution stated above, if the switching members on both the front and back sides are designed to be integrated by snap fitting, the switching members can easily be integrally mounted on both sides of the spoke portion, to thereby largely improve the facility of installation.